British defense officials say five British soldiers have been shot dead by an Afghan police officer in southern Helmand Province.

Officials say the incident occurred Tuesday when the gunman fired on the troops without warning at a police checkpoint and then fled. A joint statement from NATO and the Afghan interior ministry said six other British troops and two Afghan police were wounded in the incident.

Afghanistan's interior minister pledged a transparent investigation to track the gunman down and determine his motive for the attack. They say he may have been working with another Afghan National Policeman.

The British troops had been mentoring the police officers and living with them inside their checkpoint.

In London, British Prime Minister Gordon Brown condemned the attack, calling the deaths a "terrible loss."

Violence in Afghanistan has surged in the last year as Afghan government and foreign troops struggle to counter the Taliban insurgency.

Also Wednesday, NATO officials reported detaining several militants and capturing weapons and explosives during five operations across the country.